class A:
    # A 继承自 object 根类
    def __init__(self, a, b, c):
        self.a = a
        self.b = b
        self.c = c

    def show(self):
        print(f"A: {self.a}")
        print(f"B: {self.b}")
        print(f"C: {self.c}")


class B(A):
    def __init__(self):
        A.__init__(self, a, b, c)
        self.d = '4'

    def show(self):
        super().show()
        print(f"D: {self.d}")


if __name__ == '__main__':
    a = 1
    b = 2
    c = 3
    d = 4
    m = B()
    m.show()
